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12 February 2011 | NewScientist | 17 A NEARBY neutron star is chilling out, providing the first evidence that the cores of these collapsed stars can produce a neutron superfluid – an exotic state that cannot be created on Earth. Calculations suggest that under the intense pressure in the cores of these stars, neutrons may pair up to form a frictionless superfluid. In the process, they should release neutrinos which would pass easily through the star, carrying large amounts of energy with them. Now two teams have looked at measurements of the 330-year- old neutron star at the heart of the supernova remnant Cassiopeia A, which showed the star is losing energy by cooling exceptionally fast. Dany Page of the National Autonomous University of Mexico and Peter Shternin of Ioffe Physical Technical Institute in St Sex and aggression are bad bedfellows SEX and violence are neighbours in the brain, but they don’t get along. It turns out that the cells responsible for aggression in mouse brains are suppressed during mating, which is probably a good thing. Dayu Lin, now at New York University, and colleagues identified mouse neurons responsible for aggression and genetically manipulated them to respond to light. When the cells were stimulated, the mice instantly attacked other males, females and inanimate objects. Additional analyses revealed that several types of cells crucial for mating inhibited nearby aggression cells during sex (Nature, DOI: 10.1038/ nature09736). “The mating circuit acts like a gate on the aggression circuit and actively suppresses nearby fighting neurons when there is a potential mate around,” says Lin. Gushing flood formed giant Martian sinkhole LIKE water draining from an unplugged bathtub, meltwater flowing through deep cracks in the Martian rock may explain the origins of the enormous Hebes Chasma canyon. About 100,000 cubic kilometres of material had to be removed to form the scar, which is five times the width and depth of the Grand Canyon. But where that material went has been a mystery, as there are no surface channels through which water and sediment could have exited. John Adams of the University of Washington in Seattle and colleagues proposed in 2009 that heat from magma beneath the surface caused ice held in the rock to melt ESA/DLR/FU BERLIN (G. NEUKUM) IN BRIEF Neutron star seen forming exotic matter Petersburg, Russia, and their colleagues calculate that this can be explained if some neutrons in the core are becoming superfluid (arxiv.org/abs/1012.0045 and arxiv.org/abs/1011.6142). On Earth Superfluids with properties such as climbing up the walls of their containers can be made from chilled atoms. But the super-dense matter required for a neutron superfluid can only be made in an accelerator, and would be too hot for a superfluid to form. and released water locked up in salts. The water then drained away through underground cracks, leaving a void into which the overlying rock collapsed, to form the canyon. Now, a tabletop experiment has bolstered this theory. Martin Jackson of the University of Texas at Austin and colleagues filled a box with viscous silicone oil, representing a watery slush, and covered it with sand and small glass spheres. As the oil was allowed to drain out through slits in the box’s floor, a structure resembling Hebes Chasma appeared (Geological Society of America Bulletin, DOI: 10.1130/B30307.1). Water from the canyon may have erupted onto the surface again. This would account for a nearby valley that looks as if it was carved by water, but for which there is no other obvious source. A LIKING for sweetness might help alcoholics kick the habit. Alcohol dependence is treated using naltrexone, a drug that blocks opioid receptors in the brain, but it only works in around 78 per cent of people. David Sinclair and colleagues at the National Institute for Health and Welfare in Helsinki, Finland, asked 78 people who had taken the drug recently to rate their preference for sugar solutions. Those who favoured the least sweet were more likely to revert to drinking (Alcohol and Alcoholism, DOI: 10.1093/ alcalc/agq101). Sweet tastes and alcohol both trigger opioid chemicals that evoke pleasure. Alcoholics who prefer less sweetness may rely on another reinforcement process. On the wagon? A sweet tooth helps
